Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0-only */
2 : /*
3 : * Header file for dma buffer sharing framework.
4 : *
5 : * Copyright(C) 2011 Linaro Limited. All rights reserved.
6 : * Author: Sumit Semwal <sumit.semwal@ti.com>
7 : *
8 : * Many thanks to linaro-mm-sig list, and specially
9 : * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
10 : * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
11 : * refining of this idea.
12 : */
13 : #ifndef __DMA_BUF_H__
14 : #define __DMA_BUF_H__
15 :
16 : #include <linux/iosys-map.h>
17 : #include <linux/file.h>
18 : #include <linux/err.h>
19 : #include <linux/scatterlist.h>
20 : #include <linux/list.h>
21 : #include <linux/dma-mapping.h>
22 : #include <linux/fs.h>
23 : #include <linux/dma-fence.h>
24 : #include <linux/wait.h>
25 :
26 : struct device;
27 : struct dma_buf;
28 : struct dma_buf_attachment;
29 :
30 : /**
31 : * struct dma_buf_ops - operations possible on struct dma_buf
32 : * @vmap: [optional] creates a virtual mapping for the buffer into kernel
33 : * address space. Same restrictions as for vmap and friends apply.
34 : * @vunmap: [optional] unmaps a vmap from the buffer
35 : */
36 : struct dma_buf_ops {
37 : /**
38 : * @cache_sgt_mapping:
39 : *
40 : * If true the framework will cache the first mapping made for each
41 : * attachment. This avoids creating mappings for attachments multiple
42 : * times.
43 : */
44 : bool cache_sgt_mapping;
45 :
46 : /**
47 : * @attach:
48 : *
49 : * This is called from dma_buf_attach() to make sure that a given
50 : * &dma_buf_attachment.dev can access the provided &dma_buf. Exporters
51 : * which support buffer objects in special locations like VRAM or
52 : * device-specific carveout areas should check whether the buffer could
53 : * be move to system memory (or directly accessed by the provided
54 : * device), and otherwise need to fail the attach operation.
55 : *
56 : * The exporter should also in general check whether the current
57 : * allocation fulfills the DMA constraints of the new device. If this
58 : * is not the case, and the allocation cannot be moved, it should also
59 : * fail the attach operation.
60 : *
61 : * Any exporter-private housekeeping data can be stored in the
62 : * &dma_buf_attachment.priv pointer.
63 : *
64 : * This callback is optional.
65 : *
66 : * Returns:
67 : *
68 : * 0 on success, negative error code on failure. It might return -EBUSY
69 : * to signal that backing storage is already allocated and incompatible
70 : * with the requirements of requesting device.
71 : */
72 : int (*attach)(struct dma_buf *, struct dma_buf_attachment *);
73 :
74 : /**
75 : * @detach:
76 : *
77 : * This is called by dma_buf_detach() to release a &dma_buf_attachment.
78 : * Provided so that exporters can clean up any housekeeping for an
79 : * &dma_buf_attachment.
80 : *
81 : * This callback is optional.
82 : */
83 : void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
84 :
85 : /**
86 : * @pin:
87 : *
88 : * This is called by dma_buf_pin() and lets the exporter know that the
89 : * DMA-buf can't be moved any more. Ideally, the exporter should
90 : * pin the buffer so that it is generally accessible by all
91 : * devices.
92 : *
93 : * This is called with the &dmabuf.resv object locked and is mutual
94 : * exclusive with @cache_sgt_mapping.
95 : *
96 : * This is called automatically for non-dynamic importers from
97 : * dma_buf_attach().
98 : *
99 : * Note that similar to non-dynamic exporters in their @map_dma_buf
100 : * callback the driver must guarantee that the memory is available for
101 : * use and cleared of any old data by the time this function returns.
102 : * Drivers which pipeline their buffer moves internally must wait for
103 : * all moves and clears to complete.
104 : *
105 : * Returns:
106 : *
107 : * 0 on success, negative error code on failure.
108 : */
109 : int (*pin)(struct dma_buf_attachment *attach);
110 :
111 : /**
112 : * @unpin:
113 : *
114 : * This is called by dma_buf_unpin() and lets the exporter know that the
115 : * DMA-buf can be moved again.
116 : *
117 : * This is called with the dmabuf->resv object locked and is mutual
118 : * exclusive with @cache_sgt_mapping.
119 : *
120 : * This callback is optional.
121 : */
122 : void (*unpin)(struct dma_buf_attachment *attach);
123 :
124 : /**
125 : * @map_dma_buf:
126 : *
127 : * This is called by dma_buf_map_attachment() and is used to map a
128 : * shared &dma_buf into device address space, and it is mandatory. It
129 : * can only be called if @attach has been called successfully.
130 : *
131 : * This call may sleep, e.g. when the backing storage first needs to be
132 : * allocated, or moved to a location suitable for all currently attached
133 : * devices.
134 : *
135 : * Note that any specific buffer attributes required for this function
136 : * should get added to device_dma_parameters accessible via
137 : * &device.dma_params from the &dma_buf_attachment. The @attach callback
138 : * should also check these constraints.
139 : *
140 : * If this is being called for the first time, the exporter can now
141 : * choose to scan through the list of attachments for this buffer,
142 : * collate the requirements of the attached devices, and choose an
143 : * appropriate backing storage for the buffer.
144 : *
145 : * Based on enum dma_data_direction, it might be possible to have
146 : * multiple users accessing at the same time (for reading, maybe), or
147 : * any other kind of sharing that the exporter might wish to make
148 : * available to buffer-users.
149 : *
150 : * This is always called with the dmabuf->resv object locked when
151 : * the dynamic_mapping flag is true.
152 : *
153 : * Note that for non-dynamic exporters the driver must guarantee that
154 : * that the memory is available for use and cleared of any old data by
155 : * the time this function returns. Drivers which pipeline their buffer
156 : * moves internally must wait for all moves and clears to complete.
157 : * Dynamic exporters do not need to follow this rule: For non-dynamic
158 : * importers the buffer is already pinned through @pin, which has the
159 : * same requirements. Dynamic importers otoh are required to obey the
160 : * dma_resv fences.
161 : *
162 : * Returns:
163 : *
164 : * A &sg_table scatter list of the backing storage of the DMA buffer,
165 : * already mapped into the device address space of the &device attached
166 : * with the provided &dma_buf_attachment. The addresses and lengths in
167 : * the scatter list are PAGE_SIZE aligned.
168 : *
169 : * On failure, returns a negative error value wrapped into a pointer.
170 : * May also return -EINTR when a signal was received while being
171 : * blocked.
172 : *
173 : * Note that exporters should not try to cache the scatter list, or
174 : * return the same one for multiple calls. Caching is done either by the
175 : * DMA-BUF code (for non-dynamic importers) or the importer. Ownership
176 : * of the scatter list is transferred to the caller, and returned by
177 : * @unmap_dma_buf.
178 : */
179 : struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
180 : enum dma_data_direction);
181 : /**
182 : * @unmap_dma_buf:
183 : *
184 : * This is called by dma_buf_unmap_attachment() and should unmap and
185 : * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
186 : * For static dma_buf handling this might also unpin the backing
187 : * storage if this is the last mapping of the DMA buffer.
188 : */
189 : void (*unmap_dma_buf)(struct dma_buf_attachment *,
190 : struct sg_table *,
191 : enum dma_data_direction);
192 :
193 : /* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
194 : * if the call would block.
195 : */
196 :
197 : /**
198 : * @release:
199 : *
200 : * Called after the last dma_buf_put to release the &dma_buf, and
201 : * mandatory.
202 : */
203 : void (*release)(struct dma_buf *);
204 :
205 : /**
206 : * @begin_cpu_access:
207 : *
208 : * This is called from dma_buf_begin_cpu_access() and allows the
209 : * exporter to ensure that the memory is actually coherent for cpu
210 : * access. The exporter also needs to ensure that cpu access is coherent
211 : * for the access direction. The direction can be used by the exporter
212 : * to optimize the cache flushing, i.e. access with a different
213 : * direction (read instead of write) might return stale or even bogus
214 : * data (e.g. when the exporter needs to copy the data to temporary
215 : * storage).
216 : *
217 : * Note that this is both called through the DMA_BUF_IOCTL_SYNC IOCTL
218 : * command for userspace mappings established through @mmap, and also
219 : * for kernel mappings established with @vmap.
220 : *
221 : * This callback is optional.
222 : *
223 : * Returns:
224 : *
225 : * 0 on success or a negative error code on failure. This can for
226 : * example fail when the backing storage can't be allocated. Can also
227 : * return -ERESTARTSYS or -EINTR when the call has been interrupted and
228 : * needs to be restarted.
229 : */
230 : int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
231 :
232 : /**
233 : * @end_cpu_access:
234 : *
235 : * This is called from dma_buf_end_cpu_access() when the importer is
236 : * done accessing the CPU. The exporter can use this to flush caches and
237 : * undo anything else done in @begin_cpu_access.
238 : *
239 : * This callback is optional.
240 : *
241 : * Returns:
242 : *
243 : * 0 on success or a negative error code on failure. Can return
244 : * -ERESTARTSYS or -EINTR when the call has been interrupted and needs
245 : * to be restarted.
246 : */
247 : int (*end_cpu_access)(struct dma_buf *, enum dma_data_direction);
248 :
249 : /**
250 : * @mmap:
251 : *
252 : * This callback is used by the dma_buf_mmap() function
253 : *
254 : * Note that the mapping needs to be incoherent, userspace is expected
255 : * to bracket CPU access using the DMA_BUF_IOCTL_SYNC interface.
256 : *
257 : * Because dma-buf buffers have invariant size over their lifetime, the
258 : * dma-buf core checks whether a vma is too large and rejects such
259 : * mappings. The exporter hence does not need to duplicate this check.
260 : * Drivers do not need to check this themselves.
261 : *
262 : * If an exporter needs to manually flush caches and hence needs to fake
263 : * coherency for mmap support, it needs to be able to zap all the ptes
264 : * pointing at the backing storage. Now linux mm needs a struct
265 : * address_space associated with the struct file stored in vma->vm_file
266 : * to do that with the function unmap_mapping_range. But the dma_buf
267 : * framework only backs every dma_buf fd with the anon_file struct file,
268 : * i.e. all dma_bufs share the same file.
269 : *
270 : * Hence exporters need to setup their own file (and address_space)
271 : * association by setting vma->vm_file and adjusting vma->vm_pgoff in
272 : * the dma_buf mmap callback. In the specific case of a gem driver the
273 : * exporter could use the shmem file already provided by gem (and set
274 : * vm_pgoff = 0). Exporters can then zap ptes by unmapping the
275 : * corresponding range of the struct address_space associated with their
276 : * own file.
277 : *
278 : * This callback is optional.
279 : *
280 : * Returns:
281 : *
282 : * 0 on success or a negative error code on failure.
283 : */
284 : int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
285 :
286 : int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
287 : void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
288 : };
289 :
290 : /**
291 : * struct dma_buf - shared buffer object
292 : *
293 : * This represents a shared buffer, created by calling dma_buf_export(). The
294 : * userspace representation is a normal file descriptor, which can be created by
295 : * calling dma_buf_fd().
296 : *
297 : * Shared dma buffers are reference counted using dma_buf_put() and
298 : * get_dma_buf().
299 : *
300 : * Device DMA access is handled by the separate &struct dma_buf_attachment.
301 : */
302 : struct dma_buf {
303 : /**
304 : * @size:
305 : *
306 : * Size of the buffer; invariant over the lifetime of the buffer.
307 : */
308 : size_t size;
309 :
310 : /**
311 : * @file:
312 : *
313 : * File pointer used for sharing buffers across, and for refcounting.
314 : * See dma_buf_get() and dma_buf_put().
315 : */
316 : struct file *file;
317 :
318 : /**
319 : * @attachments:
320 : *
321 : * List of dma_buf_attachment that denotes all devices attached,
322 : * protected by &dma_resv lock @resv.
323 : */
324 : struct list_head attachments;
325 :
326 : /** @ops: dma_buf_ops associated with this buffer object. */
327 : const struct dma_buf_ops *ops;
328 :
329 : /**
330 : * @lock:
331 : *
332 : * Used internally to serialize list manipulation, attach/detach and
333 : * vmap/unmap. Note that in many cases this is superseeded by
334 : * dma_resv_lock() on @resv.
335 : */
336 : struct mutex lock;
337 :
338 : /**
339 : * @vmapping_counter:
340 : *
341 : * Used internally to refcnt the vmaps returned by dma_buf_vmap().
342 : * Protected by @lock.
343 : */
344 : unsigned vmapping_counter;
345 :
346 : /**
347 : * @vmap_ptr:
348 : * The current vmap ptr if @vmapping_counter > 0. Protected by @lock.
349 : */
350 : struct iosys_map vmap_ptr;
351 :
352 : /**
353 : * @exp_name:
354 : *
355 : * Name of the exporter; useful for debugging. See the
356 : * DMA_BUF_SET_NAME IOCTL.
357 : */
358 : const char *exp_name;
359 :
360 : /**
361 : * @name:
362 : *
363 : * Userspace-provided name; useful for accounting and debugging,
364 : * protected by dma_resv_lock() on @resv and @name_lock for read access.
365 : */
366 : const char *name;
367 :
368 : /** @name_lock: Spinlock to protect name acces for read access. */
369 : spinlock_t name_lock;
370 :
371 : /**
372 : * @owner:
373 : *
374 : * Pointer to exporter module; used for refcounting when exporter is a
375 : * kernel module.
376 : */
377 : struct module *owner;
378 :
379 : /** @list_node: node for dma_buf accounting and debugging. */
380 : struct list_head list_node;
381 :
382 : /** @priv: exporter specific private data for this buffer object. */
383 : void *priv;
384 :
385 : /**
386 : * @resv:
387 : *
388 : * Reservation object linked to this dma-buf.
389 : *
390 : * IMPLICIT SYNCHRONIZATION RULES:
391 : *
392 : * Drivers which support implicit synchronization of buffer access as
393 : * e.g. exposed in `Implicit Fence Poll Support`_ must follow the
394 : * below rules.
395 : *
396 : * - Drivers must add a read fence through dma_resv_add_fence() with the
397 : * DMA_RESV_USAGE_READ flag for anything the userspace API considers a
398 : * read access. This highly depends upon the API and window system.
399 : *
400 : * - Similarly drivers must add a write fence through
401 : * dma_resv_add_fence() with the DMA_RESV_USAGE_WRITE flag for
402 : * anything the userspace API considers write access.
403 : *
404 : * - Drivers may just always add a write fence, since that only
405 : * causes unecessarily synchronization, but no correctness issues.
406 : *
407 : * - Some drivers only expose a synchronous userspace API with no
408 : * pipelining across drivers. These do not set any fences for their
409 : * access. An example here is v4l.
410 : *
411 : * - Driver should use dma_resv_usage_rw() when retrieving fences as
412 : * dependency for implicit synchronization.
413 : *
414 : * DYNAMIC IMPORTER RULES:
415 : *
416 : * Dynamic importers, see dma_buf_attachment_is_dynamic(), have
417 : * additional constraints on how they set up fences:
418 : *
419 : * - Dynamic importers must obey the write fences and wait for them to
420 : * signal before allowing access to the buffer's underlying storage
421 : * through the device.
422 : *
423 : * - Dynamic importers should set fences for any access that they can't
424 : * disable immediately from their &dma_buf_attach_ops.move_notify
425 : * callback.
426 : *
427 : * IMPORTANT:
428 : *
429 : * All drivers and memory management related functions must obey the
430 : * struct dma_resv rules, specifically the rules for updating and
431 : * obeying fences. See enum dma_resv_usage for further descriptions.
432 : */
433 : struct dma_resv *resv;
434 :
435 : /** @poll: for userspace poll support */
436 : wait_queue_head_t poll;
437 :
438 : /** @cb_in: for userspace poll support */
439 : /** @cb_out: for userspace poll support */
440 : struct dma_buf_poll_cb_t {
441 : struct dma_fence_cb cb;
442 : wait_queue_head_t *poll;
443 :
444 : __poll_t active;
445 : } cb_in, cb_out;
446 : #ifdef CONFIG_DMABUF_SYSFS_STATS
447 : /**
448 : * @sysfs_entry:
449 : *
450 : * For exposing information about this buffer in sysfs. See also
451 : * `DMA-BUF statistics`_ for the uapi this enables.
452 : */
453 : struct dma_buf_sysfs_entry {
454 : struct kobject kobj;
455 : struct dma_buf *dmabuf;
456 : } *sysfs_entry;
457 : #endif
458 : };
459 :
460 : /**
461 : * struct dma_buf_attach_ops - importer operations for an attachment
462 : *
463 : * Attachment operations implemented by the importer.
464 : */
465 : struct dma_buf_attach_ops {
466 : /**
467 : * @allow_peer2peer:
468 : *
469 : * If this is set to true the importer must be able to handle peer
470 : * resources without struct pages.
471 : */
472 : bool allow_peer2peer;
473 :
474 : /**
475 : * @move_notify: [optional] notification that the DMA-buf is moving
476 : *
477 : * If this callback is provided the framework can avoid pinning the
478 : * backing store while mappings exists.
479 : *
480 : * This callback is called with the lock of the reservation object
481 : * associated with the dma_buf held and the mapping function must be
482 : * called with this lock held as well. This makes sure that no mapping
483 : * is created concurrently with an ongoing move operation.
484 : *
485 : * Mappings stay valid and are not directly affected by this callback.
486 : * But the DMA-buf can now be in a different physical location, so all
487 : * mappings should be destroyed and re-created as soon as possible.
488 : *
489 : * New mappings can be created after this callback returns, and will
490 : * point to the new location of the DMA-buf.
491 : */
492 : void (*move_notify)(struct dma_buf_attachment *attach);
493 : };
494 :
495 : /**
496 : * struct dma_buf_attachment - holds device-buffer attachment data
497 : * @dmabuf: buffer for this attachment.
498 : * @dev: device attached to the buffer.
499 : * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.
500 : * @sgt: cached mapping.
501 : * @dir: direction of cached mapping.
502 : * @peer2peer: true if the importer can handle peer resources without pages.
503 : * @priv: exporter specific attachment data.
504 : * @importer_ops: importer operations for this attachment, if provided
505 : * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
506 : * @importer_priv: importer specific attachment data.
507 : *
508 : * This structure holds the attachment information between the dma_buf buffer
509 : * and its user device(s). The list contains one attachment struct per device
510 : * attached to the buffer.
511 : *
512 : * An attachment is created by calling dma_buf_attach(), and released again by
513 : * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
514 : * transfer is created by dma_buf_map_attachment() and freed again by calling
515 : * dma_buf_unmap_attachment().
516 : */
517 : struct dma_buf_attachment {
518 : struct dma_buf *dmabuf;
519 : struct device *dev;
520 : struct list_head node;
521 : struct sg_table *sgt;
522 : enum dma_data_direction dir;
523 : bool peer2peer;
524 : const struct dma_buf_attach_ops *importer_ops;
525 : void *importer_priv;
526 : void *priv;
527 : };
528 :
529 : /**
530 : * struct dma_buf_export_info - holds information needed to export a dma_buf
531 : * @exp_name: name of the exporter - useful for debugging.
532 : * @owner: pointer to exporter module - used for refcounting kernel module
533 : * @ops: Attach allocator-defined dma buf ops to the new buffer
534 : * @size: Size of the buffer - invariant over the lifetime of the buffer
535 : * @flags: mode flags for the file
536 : * @resv: reservation-object, NULL to allocate default one
537 : * @priv: Attach private data of allocator to this buffer
538 : *
539 : * This structure holds the information required to export the buffer. Used
540 : * with dma_buf_export() only.
541 : */
542 : struct dma_buf_export_info {
543 : const char *exp_name;
544 : struct module *owner;
545 : const struct dma_buf_ops *ops;
546 : size_t size;
547 : int flags;
548 : struct dma_resv *resv;
549 : void *priv;
550 : };
551 :
552 : /**
553 : * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
554 : * @name: export-info name
555 : *
556 : * DEFINE_DMA_BUF_EXPORT_INFO macro defines the &struct dma_buf_export_info,
557 : * zeroes it out and pre-populates exp_name in it.
558 : */
559 : #define DEFINE_DMA_BUF_EXPORT_INFO(name) \
560 : struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
561 : .owner = THIS_MODULE }
562 :
563 : /**
564 : * get_dma_buf - convenience wrapper for get_file.
565 : * @dmabuf: [in] pointer to dma_buf
566 : *
567 : * Increments the reference count on the dma-buf, needed in case of drivers
568 : * that either need to create additional references to the dmabuf on the
569 : * kernel side. For example, an exporter that needs to keep a dmabuf ptr
570 : * so that subsequent exports don't create a new dmabuf.
571 : */
572 : static inline void get_dma_buf(struct dma_buf *dmabuf)
573 : {
574 0 : get_file(dmabuf->file);
575 : }
576 :
577 : /**
578 : * dma_buf_is_dynamic - check if a DMA-buf uses dynamic mappings.
579 : * @dmabuf: the DMA-buf to check
580 : *
581 : * Returns true if a DMA-buf exporter wants to be called with the dma_resv
582 : * locked for the map/unmap callbacks, false if it doesn't wants to be called
583 : * with the lock held.
584 : */
585 : static inline bool dma_buf_is_dynamic(struct dma_buf *dmabuf)
586 : {
587 0 : return !!dmabuf->ops->pin;
588 : }
589 :
590 : /**
591 : * dma_buf_attachment_is_dynamic - check if a DMA-buf attachment uses dynamic
592 : * mappings
593 : * @attach: the DMA-buf attachment to check
594 : *
595 : * Returns true if a DMA-buf importer wants to call the map/unmap functions with
596 : * the dma_resv lock held.
597 : */
598 : static inline bool
599 : dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)
600 : {
601 0 : return !!attach->importer_ops;
602 : }
603 :
604 : struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
605 : struct device *dev);
606 : struct dma_buf_attachment *
607 : dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
608 : const struct dma_buf_attach_ops *importer_ops,
609 : void *importer_priv);
610 : void dma_buf_detach(struct dma_buf *dmabuf,
611 : struct dma_buf_attachment *attach);
612 : int dma_buf_pin(struct dma_buf_attachment *attach);
613 : void dma_buf_unpin(struct dma_buf_attachment *attach);
614 :
615 : struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info);
616 :
617 : int dma_buf_fd(struct dma_buf *dmabuf, int flags);
618 : struct dma_buf *dma_buf_get(int fd);
619 : void dma_buf_put(struct dma_buf *dmabuf);
620 :
621 : struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,
622 : enum dma_data_direction);
623 : void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
624 : enum dma_data_direction);
625 : void dma_buf_move_notify(struct dma_buf *dma_buf);
626 : int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
627 : enum dma_data_direction dir);
628 : int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
629 : enum dma_data_direction dir);
630 :
631 : int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
632 : unsigned long);
633 : int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map);
634 : void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map);
635 : #endif /* __DMA_BUF_H__ */
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